I wanted to check if I can hear the ultrasonic components of my track "Eternal Message".

I've loaded the unmastered 32-bit float mix of my track, normalized it, limited. Then I piped the whole thing through a Glame Hihpass filter set to 18kHz with 1 pole. I did that 15 times I quess looking at the spectrogram in Audacity to ensure all the lower frequencies are long gone.Then I normalized the thing and played it back.

I heard absolutely nothing.

So I changed the sampling rate of the track from 48kHz to 8kHz. And I got this.

The original track is not yet released, it's a 140BPM breakbeat/drum'n'bass tune.